Prosecutor wants former Olympian to undergo psychiatric observation.

Prosecutor Gerry Nel said he wants the former track star to undergo an independent evaluation after a psychiatrist testified that Pistorius has an anxiety disorder stemming from his double amputation and his unstable parents, according to the CNN.com report. Dr. Meryll Vorster said Pistorius is depressed and feeling guilty after killing Reeva Steenkamp.

"Overall, Mr. Pistorius appears to be a mistrustful and guarded person," Vorster said in testimony, according to an Associated Press report.

Pistorius, who became the first amputee runner to compete in the Olympics in 2012, is on trial in Pretoria, South Africa, for the murder of his girlfriend, Steenkamp, on February 14, 2013. He pleaded not guilty to the murder and other gun charges.

Vorster testified that Pistorius had a fear of crime and since he was a double amputee, he reacted to perceived threats in different ways than other people, according to the AP report.

Nel responded by asking if Pistorius had a mental disorder, should undergo a 30-day period of observation, and if he was changing his defense to "diminished responsbility," according to the AP report.